Heat exchanger

ABSTRACT

The heat exchanger includes a first fluid path unit  10  and a second fluid path unit  9 . The first fluid path unit  10  has at least two return flow paths  26 , in which a first fluid flows, in opposed relation to each other and which are stacked continuously through folded portions  27, 18 . The second fluid path unit  9  with a second fluid flows therein has second fluid paths  22, 23  which are stacked in the stacking direction (Z direction) of the return flow paths  26  through communication units  14  to  19  and which are arranged between the return flow paths  26 . The second fluid paths  22, 23  have U-shaped flow paths in which the second fluid turns back and makes a U turn at an end  13  on the surface substantially perpendicular to Z direction. The communication units  14  to  19  communicating with the U-shaped flow paths are arranged at the other end of the second fluid path unit. Therefore, it is possible to provide a easy to assemble heat exchanger which is able to be produced efficiently.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a heat exchanger for exchanging heat between a first fluid and a second fluid or, in particular, to a heat exchanger for automotive vehicles to exchange heat between water and a refrigerant.

2. Description of the Related Art

A heat exchanger of this type is known and includes high-pressure flat tubes formed in a zigzag pattern to make up a high-pressure flow path and low-pressure flat tubes formed in a zigzag pattern to make up a low-pressure flow path, wherein three high-pressure flat tubes are formed orthogonally to each other and intertwined with three low-pressure flat tubes in an arrangement in which flows cross each other (see, for example, Japanese Unexamined Patent Publication No. 2004-184074, FIGS. 2 to 5).

The fabrication of the conventional heat exchanger described above, however, requires the step of forming a curved tube by laying the high- and low-pressure flat tubes alternately one on another to form the paths for exchanging heat with each other, thereby posing the problem that an increased number of assembly steps are required and the productivity is low.

SUMMARY OF THE INVENTION

This invention has been achieved in view of the problem described above and the object thereof is to provide a heat exchanger which is easy to assemble and is high in productivity.

In order to achieve the object described above, the technical means described below are employed. According to a first aspect of the invention, there is provided a heat exchanger comprising:

a first fluid path unit (10) including at least two return flow paths (26), in opposed relation to each other, having a flow path extending in the direction (X direction) in which the first fluid flows toward folded portions (27, 28) and a flow path in which the flow changes the direction at the folded portions (27, 28), the return flow paths (26) being stacked continuously; and

a second fluid path unit (9) having second fluid paths (22, 23) in which a second fluid flows across the first fluid are stacked through communication units (14, 15, 16, 17, 18, 19) in the stacking direction (Z direction) of the return flow paths (26), and the second fluid paths (22, 23) thus stacked being each arranged between the return flow paths (26);

wherein the second fluid paths (22, 23) each include a U-shaped flow path in which the second fluid flows in the direction (Y direction) substantially perpendicular to the flow (X direction) of the first fluid on the surface substantially perpendicular to the stacking direction (Z direction), and after turning back at one end (13) of the second fluid path unit (9), flows in the opposite direction to the substantially perpendicular direction (Y direction), and

wherein the communication units (14 to 19) communicate with the U-shaped flow paths and are arranged at the other end of the second fluid path unit (9).

In the first aspect of the invention, the communication units for establishing communication between the stacked second fluid paths communicate with the U-shaped paths, and are arranged at the other end of the second fluid path unit. By the core set operation, in which the first fluid path unit is moved from one toward the other end of the second fluid path unit and assembled on the second fluid path unit, therefore, the two fluid path units can be integrally assembled, and a heat exchanger having a high productivity is obtained. Also, each of the second fluid paths arranged between the corresponding return flow paths is configured of a U-shaped path making a U turn on the surface substantially perpendicular to the stacking direction (Z direction). Thus, a compact heat exchanger of a low height in the stacking direction, and high in both heat exchange performance and productivity, can be obtained.

According to a second aspect of the invention, there is provided a heat exchanger, comprising:

a first fluid path unit (10) including at least two return flow paths (26), in opposed relation to each other, having a flow path extending in the direction (X direction) in which the first fluid flows toward folded portions (27, 28) and a flow path in which the flow changes the direction at the folded portions (27, 28), the return flow paths (26) being stacked continuously; and

a second fluid path unit (29) having second fluid paths (32 f, 32 g) in which a second fluid flows across the first fluid are stacked through communication units (31 g) in the stacking direction (Z direction) of the return flow paths (26), and the second fluid paths (32 a, 32 g) thus stacked being each arranged between the corresponding return flow paths (26);

wherein the second fluid paths (32 a to 33 g) each include a U-shaped flow path in which the second fluid flows in the direction (Y direction) substantially perpendicular to the flow (X direction) of the first fluid, and after changing the direction at one end (32) of the second fluid path unit (29) and turning back by moving in the stacking direction (Z direction), flows in the opposite direction to the substantially perpendicular direction (Y direction), and

wherein the communication units (31 a to 31 g) communicate with the U-shaped flow paths and are arranged at the other end of the second fluid path units (29).

In the second aspect of the invention, the communication units for establishing communication between the stacked second fluid paths communicate with the U-shaped paths, and are arranged at the other end of the second fluid path unit. By moving the first fluid path unit from one end toward the other end of the second fluid path unit and assembling it on the second fluid path unit, therefore, the two fluid path units can be integrally assembled, and a heat exchanger having a high productivity is obtained. Also, a U-shaped path in which the second fluid flows in the direction opposite to the stacking direction (Z direction) is formed in each of the second fluid paths and, therefore, a compact heat exchanger of a small height in the direction of flow of the first fluid and high in heat exchange performance and productivity can be obtained.

According to a third aspect of the invention, there is provided a heat exchanger, comprising:

a first fluid path unit (10) including at least two return flow paths (26), in opposed relation to each other, having a flow path extending in the direction (X direction) in which the first fluid flows toward folded portions (27, 28) and a flow path in which the flow changes the direction at the folded portions (27, 28), the return flow paths (26) being stacked continuously;

second flow paths (34) constituting U-shaped flow paths (34) arranged between the return flow paths (26) having, in opposed relation to each other, a flow path in which the second fluid crossing the first fluid flows in from inlets (34 a, 34 c, 34 e, 34 g) and flows in the direction (counter Y direction) substantially perpendicular to the flow (X direction) of the first fluid, and a flow path turned back to change the direction and reaches outlets (34 b, 34 d, 34 f, 34 h); and

a fold member (35) having a second fluid inlet (36) and a second fluid outlet (37) and connected to the inlets (34 a, 34 c, 34 e, 34 g) and the outlets (34 b, 34 d, 34 f, 34 h);

wherein the second fluid inlet (36) and the second fluid outlet (37) communicate with each other through all the second fluid paths (34) connected to the fold member (35).

In the third aspect of the invention, the fold member is connected with the inlet and the outlet of each second fluid path, and the second fluid inlet and the second fluid outlet of the fold member communicate with each other through all the second fluid paths connected to the fold member. Therefore, a heat exchanger high in productivity in which the two fluid paths can be integrally assembled can be obtained by moving the second fluid path unit in one direction with respect to the first fluid path unit and connecting it to the fold member.

According to a fourth aspect of the invention, there is provided a heat exchanger wherein the flow paths making up the first fluid path unit (10) are flat tubes having a longitudinal surface extending in the direction (Y direction) in which the second fluid flows between the return flow paths (26).

In the fourth aspect of the invention, the heat transmission area of the first fluid paths with respect to the second fluid paths can be increased, and therefore the heat exchange performance is improved. Also, the sectional area of the second fluid paths can be increased without increasing the size of the return flow paths in the stacking direction, and therefore the pressure loss in the second fluid paths is reduced.

According to a fifth aspect of the invention, there is provided a heat exchanger, wherein the flat tubes are flat tubes having many bores formed by extrusion molding.

In the fifth aspect of the invention, the pressure resistance and the heat transmission performance of the heat exchanger are improved.

According to a sixth aspect of the invention, there is provided a heat exchanger wherein the size (h) of the gap between the return flow paths (26) making up the first fluid path unit (10) is larger than the size (t) of the return flow paths (26) in the stacking direction.

In the sixth aspect of the invention, a sharp geometrical change at the folded portions of the first fluid paths is prevented to allow an improved machinability and productivity.

According to a seventh aspect of the invention, there is provided a heat exchanger, wherein the return flow paths (26) and the second fluid paths (22, 23, 32 a to 32 g, 34) are coupled by being brazed to each other.

In the seventh aspect of the invention, the thermal resistance between the first and second fluids is reduced for an improved heat exchange performance.

According to an eighth aspect of the invention, there is provided a heat exchanger wherein the second fluid paths (22, 23, 32 a to 32 g, 34) and the first fluid paths (26) are coupled by being brazed to each other by forming a partial joint on the outer surface of the flow paths.

In the eighth aspect of the invention, the partial joint is formed on the outer surface of the flow paths for coupling by brazing, and therefore the variations of the brazed portions, such as voids, are reduced. Also, a leakage space can be formed to prevent the high-pressure fluid, which may leak, from intruding into the low-pressure fluid.

According to a ninth aspect of the invention, there is provided a heat exchanger, wherein a sacrifice corrosion layer (38) adapted to be corroded first is formed on a partially formed joint, and a space (B) in contact with the atmosphere is formed at the end portion (B) in the direction (Y direction) substantially perpendicular to the direction (X direction) in which the first fluid flows.

In the ninth aspect of the invention, should a hole be formed by the corrosion of one of the fluid paths, the sacrifice corrosion layer is corroded first and released into the atmosphere through the leakage space, thereby preventing the other fluid paths from being corroded.

According to a tenth aspect of the invention, there is provided a heat exchanger, wherein the second fluid path unit (9, 29) is formed by stacking plate members.

In the tenth aspect of the invention, the second fluid paths can be formed of segments of the same shape. Therefore, the production cost is lower, and the sectional area in the flow paths can be increased compared with the size of the second fluid path unit. Also, the overall dimensions of the flow paths can be reduced to realize a compact second fluid path unit.

According to an 11th aspect of the invention, there is provided a heat exchanger, wherein fins are arranged in the second fluid paths (22, 23, 32 a to 32 g) making up the second fluid path unit (9, 29).

In the 11th aspect of the invention, the heat transmission area can be increased for an improved heat exchange performance.

According to a 12th aspect of the invention, there is provided a heat exchanger, wherein the second fluid paths (22, 23) are formed of a pipe having a circular section.

In the 12th aspect of the invention, the number of the parts making up the flow paths can be reduced and an inexpensive heat exchanger can be provided.

According to a 13th aspect of the invention, there is provided a heat exchanger, wherein the second fluid paths (22, 23, 34) are configured of flat tubes having a flat surface in opposed relation to the outer surface of the return flow paths (26).

In the 13th aspect of the invention, a heat exchanger is produced in which the required sectional area of the flow paths is secured while, at the same time, reducing the length of the return flow paths in the stacking direction (Z direction).

According to a 14th aspect of the invention, there is provided a heat exchanger, wherein a partitioning member (39) is arranged in the second fluid paths (32 a to 32 g) and U-shaped flow paths are formed in which the flow is turned back before and after the partitioning member (39).

In the 14th aspect of the invention, the thickness of the U-shaped paths can be reduced to realize a compact heat exchanger with an improved heat exchange performance.

According to a 15th aspect of the invention, there is provided a heat exchanger, wherein the second fluid paths (34) are formed as U-shaped flat tubes communicating in the stacking direction (Z direction) of the return flow paths (26), and open ends of a plurality of the U-shaped flat tubes arranged in the same direction (Z direction) are inserted between the return flow paths (26) and further connected to the fold member (35).

In the 15th aspect of the invention, the second fluid path unit is formed of component parts comparatively simple in shape and therefore a heat exchanger high in machinability and easy to assemble is provided.

According to a 16th aspect of the invention, there is provided a heat exchanger, wherein the U-shaped flat tubes are arranged in two rows in the direction (X direction) of the flow of the first fluid and the positions at which the two rows of the U-shaped flat tubes are connected to the fold member (35) are staggered in stacking direction (Z direction).

In the 16th aspect of the invention, the flow paths of the second fluid path unit can be lengthened and therefore the heat exchange performance can be improved.

The reference numerals in the parentheses following each means described above indicate an example of correspondence with specific means included in the embodiments described later.

The prevent invention may be more fully understood from the description of preferred embodiments of the invention, as set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of the refrigeration cycle including a water-refrigerant heat exchanger and an internal heat exchanger according to a first embodiment.

FIG. 2 is an exploded perspective view showing the state before the heat exchanger according to the first embodiment is assembled.

FIG. 3 is a perspective view showing a configuration of the heat exchanger according to the first embodiment.

FIG. 4 is an exploded perspective view showing a configuration of a heat exchanger after assembling a first fluid path unit and a second fluid path unit shown in FIG. 2.

FIG. 5 is an exploded perspective view showing a configuration of a heat exchanger with fins arranged in the second fluid path according to a first embodiment.

FIG. 6 is an exploded perspective view showing the state before the heat exchanger according to the second embodiment is assembled.

FIG. 7 is an exploded perspective view showing a configuration of a heat exchanger after assembling a first fluid path unit and a second fluid path unit shown in FIG. 6.

FIG. 8 is an exploded perspective view showing the internal configuration of the second fluid path of the heat exchanger according to the second embodiment.

FIG. 9 is an exploded perspective view showing the state of the heat exchanger according to a third embodiment before being assembled.

FIG. 10 is a perspective view showing the relation between the gap size between the return flow paths of the first fluid path unit and the height of the particular flow paths of the heat exchanger according to the first, second and third embodiments.

FIG. 11 is a sectional view schematically showing the joint between the flow paths of the first and second fluid path units of the heat exchanger according to the first, second and third embodiments.

FIG. 12 is a schematical sectional view taken in line A-A in FIG. 11.

FIG. 13 is a perspective view showing the state before assembling of a heat exchanger according to a modification of the third embodiment.

FIG. 14 is a perspective view showing a first modification of the second fluid path unit of the heat exchanger according to the first embodiment.

FIG. 15 is a perspective view showing a second modification of the second fluid path unit of the heat exchanger according to the first embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

The heat exchanger according to this embodiment is operated to exchange heat between two fluids flowing in a first fluid path and a second fluid path, respectively, and is used, for example, for exchanging heat between water and a refrigerant in the air-conditioning cycle. With the heat exchanger according to this embodiment, the heat released by an outdoor unit is discharged into the engine water so that the water temperature is increased to improve the engine warming speed on the one hand and the compartment heating performance on the other hand during the time when the water temperature is not sufficiently high immediately after starting the engine. Further, the heat exchanger according to this embodiment can be used as an internal heat exchanger, for example, in the air-conditioning cycle. In the application as an internal heat exchanger, heat is exchanged between the refrigerant downstream of an outdoor gas cooler and the refrigerant downstream of an evaporator in the air-conditioning cycle using the CO₂ refrigerant. Thus, the temperature of the refrigerant upstream of an expansion valve can be reduced, resulting in an increased enthalpy difference in the evaporator.

The heat exchanger according to this embodiment is explained below. FIG. 1 is a schematic diagram showing a configuration of the refrigeration cycle having a water-refrigerant heat exchanger and an internal heat exchanger according to this embodiment. FIG. 2 is an exploded perspective view showing a configuration of the heat exchanger after assembling a first fluid path unit 10 and a second fluid path unit 9. FIG. 3 is a perspective view showing a configuration of the heat exchanger according to this embodiment. FIG. 4 is an exploded perspective view showing the internal configuration of the second fluid paths of the heat exchanger according to this embodiment. FIG. 5 is an exploded perspective view showing the configuration with fins arranged in the second fluid paths shown in FIG. 4.

Next, the configuration of the refrigeration cycle shown in FIG. 1 will be explained. This refrigeration cycle uses carbon dioxide (CO₂) as a refrigerant. A high-temperature high-pressure gas refrigerant compressed to about 15 MPa by a compressor 1 is cooled by releasing heat into the engine cooling water flowing through a warm water circuit W in a water-refrigerant heat exchanger 2. The gas refrigerant is further cooled by passing through a gas cooler 3 and an internal heat exchanger 4 making up a refrigerant circuit R. The gas cooler 3 functions as a radiator of the refrigerant circuit R.

The internal heat exchanger 4 is for exchanging heat between the refrigerant cooled by the gas cooler 3 and the low-temperature refrigerant which has exchanged heat with the evaporator 6. The CO₂ refrigerant has a larger specific heat capacity at constant pressure than the conventional R134a refrigerant. Thus, the dryness at the inlet of the evaporator 6 increases, and the enthalpy difference between inlet and outlet of the evaporator 6 decreases, thereby reducing the air cooling capacity of the evaporator 6.

In view of this, heat is exchanged through the internal heat exchanger 4 between the refrigerant cooled by the gas cooler 3 and the refrigerant which has exchanged heat in the evaporator 6 to thereby increase the enthalpy difference between inlet and outlet of the evaporator 6 for an improved cooling capacity. The refrigerant that has flowed out of the internal heat exchanger 4 is reduced in pressure to about 5 MPa in the decompressor 5 and then flows into the evaporator 6.

The evaporator 6 for the refrigerant circuit R exchanges heat with the air, so that the liquid refrigerant is evaporated to become a low-temperature gas refrigerant. The low-temperature gas refrigerant that has flowed out of the evaporator 6 provisionally flows into an accumulator 7 and is separated into gas and liquid. Only the gas refrigerant receives heat, in the internal heat exchanger 4, from the high-temperature refrigerant flowing out of the gas cooler 3 and is sent to the compressor 1.

Next, the warm water circuit W includes a heater core 8 making up a compartment-heating heat exchanger which exchanges heat between the engine cooling water heated by the engine, not shown, and the air in the compartments. The water-refrigerant heat exchanger 2 is connected before the heater core 8.

The water-refrigerant heat exchanger 2 is for exchanging heat between the engine cooling water supplied from the engine and the high-temperature high-pressure gas refrigerant compressed in the compressor 1. The engine cooling water, after exchanging heat in the water-refrigerant heat exchanger 2, returns to the engine through the heater core 8.

Next, the water-refrigerant heat exchanger 2 and the internal heat exchanger 4 are explained. The heat exchangers 2, 4 according to this embodiment are each configured of a first fluid path unit 10 allowing a first fluid to flow therein and a second fluid path unit 9 allowing a second fluid to flow therein. These flow paths are assembled in an opposed relation to each other so that the fluids flowing in these units exchange heat with each other. The first and second fluids, which may be of various types, are assumed to be a refrigerant and water, respectively, by way of explanation.

The first fluid path unit 10 includes folded portions 27, 28 by which the first fluid flowing therein turns back and changes the direction and which form return flow paths 26 in opposed relation to each other. The folded portions 27, 28 are formed at two or more positions. In the first fluid path unit 10, the return flow paths 26 are continuously stacked through the folded portions 27, 28 thereby to form a zigzag flow path.

The first fluid path unit 10 includes, at the upper part in the stacking direction of the return flow paths 26, i.e. in Z direction in FIG. 2, an inflowing refrigerant tank 24 into which the first fluid flows. The first fluid path unit 10 includes an outflowing refrigerant tank 25, on the same side as the inflowing refrigerant tank 24 side, after four folded portions 28 arranged in the direction in which the first fluid flows from the inflowing refrigerant tank 24, i.e. in X direction in FIG. 2 and three folded portions 27 arranged on the same side as the inflowing refrigerant tank 24. A predetermined gap is formed between the adjacent return flow paths 26 arranged substantially in parallel along the X direction in FIG. 2.

The flow paths making up the first fluid path unit 10 are flat tubes having a longitudinal surface extending in the direction of flow of the second fluid when exchanging heat with the first fluid, i.e. when flowing between the return flow paths 26, that is to say, in Y direction in FIG. 2. The first fluid path unit 10 is configured of a serpentine tube by bending the flat tube. This flat tube may alternatively be a flat tube having many bores formed by extrusion molding.

Each folded portion 27, 28 is formed with an arcuate bend of at least 180° having a predetermined radius to prevent the bend having an excessively sharp angle. The diameter of the arc making up the folded portion is desirably a size taking the material, thickness and outer diameter of the tube into consideration.

The second fluid path unit 9 is configured of a stack tubes of what is called the drawn cup type. The second fluid path unit 9 has a U-shaped path into which the second fluid flows in the direction (Y direction in FIG. 2) substantially perpendicular to the direction (X direction) of flow of the first fluid, and after turning back at one end 13, flows in the direction opposite to the Y direction. The inlet 19 and the outlet 20 of the U-shaped flow path are arranged at the other end of the second fluid path unit 9. The second fluid path unit 9 is configured of the second fluid paths having this configuration in a plurality of layers in Z direction in FIG. 2. The second fluid path 23 a and the second fluid path 23 b adjacent to each other in the same direction as Z direction communicate with each other through a communication unit 14 on the inlet 19 and the outlet 20 sides.

The inlet 11 and the outlet 21 of the second fluid path unit 9 are arranged at the other end of the second fluid path unit 9. The second fluid paths 23 a, 23 b, 23 c, 23 d, 23 e, 23 f and 23 g are stacked in such a manner that the interior thereof communicate with each other through the communication units 14, 15, 16, 17, 18, 19 arranged on the inlet 11 and outlet 21 sides. The communication units 14 to 19, the inlet 11 and the outlet 21 are arranged at the other end of the second fluid path unit 9.

The second fluid paths 23 a to 23 g are supported like cantilevers at the other end of the second fluid path unit 19. The interior of each of the second fluid paths 23 a to 23 g communicates through the communication units 14 to 19 at the other end of the second fluid path unit 9, and the communication units adjacent to each other in X direction are coupled to each other integrally. On the unsupported side of the second fluid paths 23 a to 23 g, i.e. at one end 13 of the second fluid path unit 9, gaps are formed between the adjacent ones of the second fluid paths 23 a to 23 g in a sufficient size that the flow paths of the first fluid path unit 10 can be inserted therein when assembling the first fluid path unit 10 and the second fluid path unit 9. These gaps are formed substantially uniformly up to the communication units 14 to 19 arranged at the other end of the second fluid path unit 9.

The second fluid paths 22, 23 stacked in a plurality of layers each forming a U-shaped path having at least one U turning point on the surface substantially perpendicular to Z direction. In other words, as the inlet 19 and the outlet 20 of the second fluid are arranged on the same side, the folded portions of the U-shaped flow path making a U turn are arranged at an odd number of points, say, one or three points, in each of the second fluid paths 22, 23.

In the second fluid path unit 9, the second fluid paths 23 a to 23 g and the communication units 14 to 19 are formed and fabricated by stacking plate members of a predetermined shape of aluminum or aluminum alloy. The second fluid paths 23 a to 23 g are fabricated to form a predetermined U-shaped path by stacking the plate members.

The second fluid paths, as shown in FIG. 4, are so configured that an upstream flow path member and a downstream flow path member constituted of plate members are laid and brazed one on the other to form a predetermined flow path therebetween and integrally coupled to each other by brazing. The internal structure of the flow path is explained by taking the second fluid paths 23 b as an example. The upstream flow path member 14 b has a substantially central partitioning member 14 d extending in the direction (Y direction) substantially perpendicular to the direction (X direction) of flow of the first fluid. In an area representing about one half of an end of the upstream flow path member 14 b, a communication hole 14 c making up the communication unit 14 into which the second fluid flows from the second fluid path 23 a is formed. In the area representing about one half of an end of the downstream flow path member 15 a, on the other hand, a communication hole 15 c making up the communication unit 15 is formed into which the second fluid flows and which forms a U-shaped flow from the communication hole 14 c.

Also, at least one of the inner and outer surfaces of the upstream flow path member 14 b and the downstream flow path member 15 a is corrugated, thereby contributing to an increased heat transmission area. Especially in the case where the outer surface is corrugated, the top of the wave of a wave corresponds to a coupling between the second fluid path and the second fluid path. The upstream flow path member 14 b and the downstream flow path member 15 a are laid and coupled one on the other. In this way, a partitioning unit 14 d comes into contact with the reverse surface of the downstream flow path member 15 a thereby to form a U-shaped flow path in the second fluid path 23 b.

Further, as shown in FIG. 5, two fins 55 may be interposed between the upstream flow path member 14 b and the downstream flow path member 15 a with the partitioning unit 14 d therebetween thereby to form a second fluid path 23 b. The second fluid path unit 9 is formed by stacking and coupling a plurality of the second fluid paths in Z direction by the communication units 14, 15, 16, 17, 18, 19.

The distance between the return flow paths 26 is larger than the height of the second fluid paths 22, 23 in Z direction. This size difference eases the job of inserting each of the second fluid paths between the corresponding return flow paths 26 when assembling the first fluid path unit 10 and the second fluid path unit 9. The first fluid path unit 10 and the second fluid path unit 9 having this configuration are assembled by, as shown in FIG. 3, in such a manner that the second fluid paths 22, 23 a to 23 g are arranged in opposed relation to the return flow paths 26 in each gap between the return flow paths 26. In this way, the first fluid path unit 10 and the second fluid path unit 9 are formed integrally as one box-like object constituting one heat exchanger. These return flow paths 26 and the second fluid paths 22, 23 a to 23 g are coupled by being brazed to each other after forming the joint between them by applying an external force using a jig or the like from both vertical sides of the heat exchanger

Next, the flow of the second fluid in the second fluid path unit 9 will be explained. The engine cooling water, as an example of the second fluid, flows in by way of the inlet 11 and through the inlet 12 of the second fluid path 22, flows in Y direction, and after making a U turn at the folded portion 13 on a surface substantially perpendicular to Z direction, reaches the outlet of the adjacent second fluid path 23 a. The engine cooling water moves in Z direction from the outlet through the communication unit 14 and flows into the second fluid path 23 b. Further, the engine cooling water flowing in Y direction through the second fluid path 23 b, after making a U turn on the surface substantially perpendicular to Z direction, reaches the outlet of the adjacent second fluid path 22. In the process, the engine cooling water making a U turn flows in the opposite direction to the flow making a U turn in the second fluid path 23 a from the second fluid path 22. After that, the engine cooling water moves in Z direction from the outlet through the communication unit 15, and flows into the second fluid path 22. Further, the engine water runs in Y direction and, after making a U turn on the surface substantially perpendicular to Z direction, reaches the outlet of the adjacent second fluid path 23 c. In the process, the engine cooling water makes a U turn in the same direction of flow as when making a U turn in the second flow path 23 a from the second fluid path 22.

After that, the engine cooling water flows sequentially, by changing the direction of U turn, until it flows out from the outlet 21. Specifically, the engine cooling water subsequently forms a flow passing through the communication unit 16, the second fluid path 23 d, the second fluid path 22, the communication unit 17, the second fluid path 22, the second fluid path 23 e, the communication unit 18, the second fluid path 23 f, the second fluid path 22, the communication unit 19, the second fluid path 22, the second fluid path 23 g and the outlet 20 in that order. During this sequential flow, the engine cooling water exchanges heat with the refrigerant flowing in the return flow paths 26 of the first fluid path unit 10.

As described above, the heat exchanger according to this embodiment includes the first fluid path unit 10 having at least two return flow paths 26 in opposed relation to each other in which the first fluid flows in opposite directions through the folded portions 27, 28, and configured by continuously stacking the return flow paths 26, and the second fluid path unit 9 in which the second fluid paths 22, 23 with the second fluid flowing therein are stacked through the communication units 14 to 19 in the same direction as the stacking direction (Z direction) of the return flow paths 26 and each of the second fluid paths 22, 23 is arranged between the return flow paths 26. The second fluid paths 22, 23 have a U-shaped flow path forming the flow of the second fluid turning back at one end 13 of the second fluid path unit 9 on the surface substantially perpendicular to Z direction. Further, the communication units 14 to 19 communicate with the U-shaped flow paths 34 and are arranged at the other end of the second fluid path unit 9.

In this configuration, the communication units 14 to 19 for establishing communication between the stacked second fluid paths communicate with the U-shaped flow paths 34 while being arranged at the other end of the second fluid path unit 9. Thus, heat exchangers 2, 4 efficient to be produced can be obtained in which, by moving the first fluid path unit 10 from the one end 13 toward the other end of the second fluid path unit 9 and assembling it on the second fluid path unit 9, the two fluid path units can be assembled integrally. Also, compact, heat exchangers 2, 4 efficient to be produced lower in height in Z direction and high in heat exchange performance can be obtained in which the second fluid paths arranged between the return flow paths 26 are each configured of a U-shaped flow path making a U turn on the surface substantially perpendicular to Z direction.

Also, the flow paths making up the first fluid path unit 10 are configured of a flat tube having longitudinal surfaces extending in the direction (Y direction) of flow of the second fluid between the return flow paths 26. As long as this configuration is employed, the heat transmission area of the first and second fluid paths can be increased for an improved heat exchange performance. Also, as the sectional area of the second fluid paths 22, 23 can be increased without increasing the size of the return paths 26 in stacking direction (Z direction), the pressure loss in the second fluid paths can be reduced.

The flat tube may be a flat tube having many bores formed by extrusion molding, in which case the pressure resistance and the heat transmission performance of the heat exchanger are improved.

Also, in the case where this configuration is employed while brazing the return flow paths 26 and the second fluid paths 22, 23 to each other, the heat resistance between the first and second fluids is reduced for an improved heat exchange performance.

The second fluid path unit 9 is formed by stacking plate members. In the case where this configuration is employed, the second fluid paths 22, 23 can be formed of segments of the same shape and, therefore, the cost can be decreased while, at the same time, increasing the sectional area in the flow paths as compared with the size of the second fluid path unit 9. Also, the outer dimensions of the flow paths can be reduced and therefore the overall size of the second fluid path unit 9 can be reduced.

In the case where fins 55 are arranged in the second fluid paths 22, 23 making up the second fluid path unit 9, the heat transmission area is increased and the heat exchange performance improved.

Second Embodiment

As a second embodiment, a heat exchanger 30 having a different form of the second fluid path unit in the configuration of the heat exchanger according to the first embodiment is explained with reference to FIGS. 6 to 8. FIG. 6 is an exploded perspective view showing a configuration of the heat exchanger 30 according to this embodiment. FIG. 7 is a perspective view showing the configuration of the heat exchanger after assembling the first fluid path unit 10 and the second fluid path unit 29. FIG. 8 is an exploded perspective view showing the internal configuration of the second fluid paths in the heat exchanger according to this embodiment.

This heat exchanger 30, like the heat exchanger according to the first embodiment, is used as the water-refrigerant heat exchanger 2 and the internal heat exchanger 4 shown in FIG. 1. The heat exchanger 30 is configured of the first fluid path unit 10 in which the first fluid flows and the second fluid path unit 29 in which the second fluid flows. These units are assembled with the flow paths thereof in an opposed relation to each other to exchange heat between the fluids flowing in the two units. The first and second fluids, as in the first embodiment, are a refrigerant and water, respectively.

The first fluid path unit 10 according to this embodiment is identical with the first fluid path unit 10 of the heat exchanger according to the first embodiment.

The second fluid path unit 29 is configured of the stacked tube of the drawn-cup type. The second fluid path unit 29 includes second fluid paths 32 a, 32 b, 32 c, 32 d, 32 e, 32 f, 32 g stacked in a plurality of layers in Z direction in FIG. 6. In the second fluid paths, U-shaped flow paths are formed in which the second fluids 32 a to 32 g flow from a direction substantially perpendicular to the direction (Y direction) of the first fluid and, after changing the direction at one end 32 of the second fluid path unit 29 and returning by moving in the stacking direction (Z direction), flow in the direction opposite to the Y direction. In other words, this U-shaped flow path is such that the second fluid makes a U turn at the one end 32 in the second fluid paths 32 a to 32 g and flows in the opposite direction through two substantially vertical spaces.

The second fluid path unit 9 has the inlet 11 and the outlet 20 thereof arranged at the other end 31 of the second fluid path unit 9. The second fluid paths 32 a to 32 g are stacked in such a manner as to establish communication to each other through the communication units 31 a, 31 b, 31 c, 31 d, 31 d, 31 f, 31 g arranged on the side of the second fluid path 9 at the inlet 11 and the outlet 21.

Also, the second fluid paths 32 a to 32 g are supported like a cantilever on the side where the inlet 11 and outlet 21 side are arranged, i.e. at the other end of the second fluid path unit 29. The second fluid paths 32 a to 32 g internally communicate with each other through the communication units 31 a to 31 g, respectively, at the other end 31 of the second fluid path unit 29, while, at the same time, integrally coupling the communication units adjacent in X direction to each other integrally.

On the side of the second fluid path unit 29 where the second fluid paths 32 a to 32 g are not supported, i.e. at the one end 31 of the second fluid path unit 29, gaps, into which the flow paths of the first fluid path unit 10 can be inserted when assembling the first fluid path unit 10 and the second fluid path unit 29 are assembled, are formed between the corresponding ones of the second fluid paths 32 a to 32 g. These gaps are formed substantially uniformly up to the communication units 31 a to 31 g arranged at the other end of the second fluid path unit 29.

The second fluid path unit 29 is formed by stacking plate members of aluminum or aluminum alloy of a predetermined shape. Each of the second fluid paths is formed with a U-shaped flow path, as described above, by laying the plate members one on another.

The second fluid paths, as shown in FIG. 8, are configured integrally by laying and brazing an upstream flow path member and a downstream flow path member formed of plate members through a partitioning plate to form a predetermined U-shaped flow path between the upstream flow path member and the downstream flow path member. The internal configuration of the flow paths is explained taking the second fluid paths 33 as an example. A communication hole 33 c into which the second fluid flows from the inlet 11 of the second fluid path unit 29 is formed at one end of the upstream flow path member 33 a. Also, a communication hole 33 d into which the second fluid flows, as a U-shaped flow, from the communication hole 33 c is formed at one end of the downstream flow path member 33 b.

A partitioning plate 39 forming a U-shaped flow path is arranged in the second fluid paths 32 a to 32 g. The partitioning plate 39 includes a communication hole 39 a providing a path for a U turn at the other end far from the communication hole 33 c in the upstream flow path member 33 a. At least one of the inner and outer surfaces of the upstream flow path member 33 a and the downstream flow path member 33 b is corrugated, thereby contributing to an increased heat transmission area. Especially, in the case where the outer surface is corrugated, the top of a wave corresponds to the joint between the first fluid paths and the second fluid paths. The upstream flow path member 33 a and the downstream flow path member 33 b are laid and coupled one on another, so that the partitioning plate 39 is fixed between them and U-shaped flow paths are formed in the second fluid paths 33. Further, a fin 41 may be interposed between the partitioning plate 39 and the upstream flow path member 33 a and a fin 40 between the partitioning plate 39 and the downstream flow path member 33 b thereby to form the second fluid paths 33. In the second fluid path unit 29, a plurality of the second fluid paths formed in this way are coupled to each other through the communication units 31 a, 31 b, 31 c, 31 d, 31 e, 31 f, 31 g and stacked in Z direction.

The distance between the return flow paths 26 is larger than the height of the second fluid paths 32 a to 32 g in Z direction. This difference makes it possible to easily carry out the job of inserting each second fluid path in the corresponding gap between the return flow paths 26 when assembling the first fluid path unit 10 and the second fluid path unit 29.

The first fluid path unit 10 and the second fluid path unit 29 having this configuration, as shown in FIG. 7, are assembled in such a manner that the second fluid paths 32 a to 32 g are arranged in opposed relation to the return flow paths 26 in the gap between the return flow paths 26. In this way, the first fluid path unit 10 and the second fluid path unit 29 are integrally formed as a single box-like mass to make up one heat exchanger. The return flow paths 26 and the second fluid paths 32 a to 32 g are coupled to each other by brazing after forming the joints thereof by applying an external force from two vertical sides of the heat exchanger using a jig or the like.

Next, the flow of the second fluid in the second fluid path unit 29 is explained. The engine cooling water as an example of the second fluid flows in by way of the inlet 11 and, after advancing in Y direction through the second fluid path 32 a and changing direction at the folded portion 32, moves in the Z direction and turns back, after which it flows in the direction opposite to the Y direction and reaches the communication unit 31 a for the adjacent second fluid path 32 b in Z direction. The engine cooling water moves in the Z direction through the communication unit 31 a and flows into the second fluid path 32 b. Further, the engine cooling water, advancing in the Y direction through the second fluid path 32 b and changing direction at the folded portion 32, moves in the Z direction and turns back, after which it flows in the direction opposite to the Y direction and reaches the communication unit 31 b for the adjacent second fluid path 32 c in Z direction. After that, the engine cooling water, repeating a U turn before flowing out from the outlet 31, flows in the Z direction. Specifically, the engine cooling water subsequently flows through the communication unit 31 b, the second fluid path 32 c, the folded portion 32, the communication unit 31 c, the second fluid path 32 d, the folded portion 32, the communication unit 31 d, the second fluid path 32 e, the folded portion 32, the communication unit 31 e, the second fluid path 32 f, the folded portion 32, the communication unit 31 f, the second fluid path 32 g, the communication unit 31 g and the outlet 21 in that order. During this flow, the engine cooling water exchanges heat with the refrigerant flowing through the return flow paths 26 of the first fluid path unit 10.

As described above, the heat exchanger according to this embodiment includes a first fluid path unit 10 having at least two return flow paths 26 in opposed relation to each other in which the first fluid flows in opposite directions through the folded portions 27, 28 and in which the return flow paths 26 are continuously stacked through the folded portions 27, 28, and a second fluid path unit 29 in which the second flow paths 32 a to 32 g with the second fluid flowing therein are stacked through the communication units 31 a to 31 g in the stacking direction (Z direction) of the return flow paths 26 and in which the stacked second fluid paths 32 a to 32 g are each arranged between the corresponding return flow paths 26. The second fluid paths 32 a to 32 g each have therein a U-shaped flow path in which the second fluid flows from the direction (Y direction) substantially perpendicular to the flow (X direction) of the first fluid and, after changing direction at one end 32 of the second fluid path unit 29, moving in the stacking direction (Z direction) and turning back, flows in the direction opposite to the direction (Y direction) substantially perpendicular thereto. Further, the communication units 31 a to 31 g, communicating with the U-shaped path, are arranged at the other end 31 of the second fluid path unit 29.

With this configuration, the communication units 14 to 19 for establishing communication between the stacked second fluid paths 32 a to 32 g communicate with the U-shaped flow paths and are arranged at the other end of the second fluid path unit 29. Therefore, by moving the first fluid path unit 10 from one end to the other end of the second fluid path unit 29 and assembling it on the second fluid path unit 29, the two fluid path units can be integrally assembled, thereby making it possible to easily produce a heat exchanger 30. Also, the U-shaped path is formed in which the second fluid forms the flow opposite to the stacking direction (Z direction), and therefore a compact heat exchanger 30 low in height along the direction of flow of the first fluid and high in heat exchange performance and productivity can be produced.

Also, in the case where the return flow paths 26 and the second fluid paths 32 a to 32 g are coupled by brazing to each other, the heat resistance between the first and second fluids can be reduced for an improved heat exchange performance.

The second fluid path unit 29 is formed by stacking plate members. In the case where this configuration is employed, the second fluid paths 32 a to 32 g can be formed using the segments of the same shape. Therefore, the cost is reduced and the sectional area of the flow path can be reduced as compared with the size of the second fluid path unit 29. Also, as the outer dimensions of the flow path can be reduced, the second fluid path unit 29 as a whole can be reduced in size.

Also, the second fluid paths 32 a to 32 g have an internal partitioning plate 39 therein, and a U-shaped path is formed to return the flow before and after the partitioning plate 39. In the case where this configuration is employed, the thickness of the U-shaped flow path can be reduced, thereby making it possible to reduce the size and improve the heat exchange performance of the heat exchanger 30.

In the case where the fins 40, 41 are arranged in the second fluid paths 32 a to 32 g making up the second fluid path unit 29, the heat transmission area is increased and the heat exchange performance improved.

Third Embodiment

A heat exchanger according to the third embodiment having a different form of the second fluid path unit in the configuration of the heat exchangers according to the first and second embodiments is explained below with reference to FIG. 9. FIG. 9 is an exploded perspective view showing the heat exchanger according to this embodiment in the state before being assembled.

The heat exchanger according to this embodiment, like the heat exchangers according to the first and second embodiments, is used as the water-refrigerant heat exchanger 2 and the internal heat exchanger 4 shown in FIG. 1. This heat exchanger is configured of a first flow path unit 10 in which the first fluid flows and a second flow path unit in which the second fluid flows, and assembled with the flow paths of the two units in opposed relation to each other to exchange heat between the fluids flowing in the two units. The first and second fluids, like in the first and second embodiments, are assumed to be a refrigerant and water, respectively, by way of explanation.

The first fluid path unit 10 according to this embodiment is identical with the first fluid path unit 10 of the heat exchangers according to the first and second embodiments.

The second fluid path unit according to this embodiment is configured of a plurality of U-shaped flow paths 34 making up the second fluid paths and a folded member 35 connected to the U-shaped flow paths 34. In the U-shaped flow paths 34, the second fluid flows in from the inlets 34 a, 34 c, 34 e, 34 g in the direction substantially perpendicular to the direction (X direction) of flow of the first fluid and turns back, after which it makes a U turn, by flowing in the opposite direction, and flows out from the outlets 34 b, 34 d, 34 f, 34 h. The second fluid path is configured of at least one U-shaped path 34 arranged in the stacking direction (Z direction in FIG. 9) of the return flow paths 26. A gap into which the flow paths of the first fluid path unit 10 can be inserted is formed between the opposed U-shaped flow paths 34.

The folded member 35 includes twice as many connection ports as the U-shaped flow paths 34 on the side surface thereof, and constitutes a box-like member functioning as a tank having a second fluid inlet 36 as an entrance of the second fluid and a second fluid outlet 37 as an exit of the second fluid. The connection ports formed on the side surface of the folded member 35 include, from the bottom up, a connection port 35 a, a connection port 35 b, a connection port 35 c, a connection port 35 d, a connection port 35 e, a connection port 35 f, a connection port 35 g and a connection port 35 h in that order. A partitioning plate is arranged between the connection port 35 a and the connection port 35 b, between the connection port 35 c and the connection port 35 d, between connection port 35 e and the connection port 35 f, and between the connection port 35 g and the connection port 35 h. No partitioning plate is arranged, and communication is established through the interior of the box-like body of the folded member 35 between, the connection port 35 b and the connection port 35 c, between the connection port 35 d and the connection port 35 e and between connection port 35 f and the connection port 35 g. The folded member 35 is formed by combining and brazing plate members made of aluminum or an aluminum alloy.

The size between the return flow paths 26 is larger than the height of the U-shaped flow path 34 in the Z direction. This size difference makes it possible to easily carry out the job of inserting each U-shaped flow path 34 between the corresponding return flow paths 26 when assembling the first fluid path unit 10, the U-shaped flow paths 34 and the folded member 35.

An example of assembly of the first fluid path unit 10, the U-shaped flow paths 34 and the folded member 35 is described below. The outlet 34 h of the uppermost U-shaped flow path 34 is passed above the uppermost return flow path 26, and the outlet 34 g is inserted in the Y direction between the uppermost return flow paths 26 and advanced in Y direction until it reaches the connection port of the folded member 35. The outlet 34 h is connected to the connection port 35 h, and the inlet 34 g to the connection port 35 g. The operation is similarly for the other U-shaped flow paths 34. Specifically, the second uppermost U-shaped flow path 34 is inserted between the return flow paths 26, and the outlet 34 f is connected to the connection port 35 f, while the inlet 34 e is connected to the connection port 35 e. Also, the third uppermost U-shaped flow path 34 is inserted between the return flow paths 26, and the outlet 34 d is connected to the connection port 35 d, while the inlet 34 c is connected to the connection port 35 c. The lowest U-shaped flow path 34 is inserted between the return flow paths 26, and the outlet 34 b is connected to the connection port 35 b, while the inlet 34 a is connected to the connection port 35 a. The return flow paths 26 and the U-shaped flow path 34, after applying an external force therefore from the two sides of the heat exchanger in vertical direction by a jig or the like and thus securing the joint between the two flow paths, are coupled by brazing and fixed. In similar fashion, each outlet and inlet of the U-shaped flow paths 34 and each connection port of the folded member 35 are coupled by brazing.

The U-shaped flow paths 34 configured in this way and the first fluid path unit 10 and the second fluid path unit configured of the folded member 35 are integrally formed as one box-like object and make up a heat exchanger having considerable overall strength.

Next, the flow of the second fluid in the second fluid path unit is explained. The engine cooling water as an example of the second fluid flows into the folded member 35 from the second fluid inlet 36, and from the inlet 34 a enters the lowest U-shaped flow path through the connection port 35 a. After making a U turn, the second fluid flows in Y direction, and through the connection port 35 b, flows out from the outlet 34 b and flows into the folded member 35. Further, the engine cooling water enters the second lowest U-shaped flow path from the inlet 34 c through the connection port 35 c and, by making a U turn, flows in the Y direction, after which it passes through the connection port 35 d, flows out of the outlet 34 d and flows into the folded member 35. Then, the engine cooling water enters the third lowest U-shaped flow path through the connection port 35 e from the inlet 34 e, and after making a U turn and flowing in the Y direction, flows out of the outlet 34 f through the connection port 35 f and flows into the folded member 35. The engine cooling water enters the uppermost U-shaped flow path through the connection port 35 g from the inlet 34 g, and after making a U turn and flowing in the Y direction, flows out from the outlet 34 h through the connection port 35 h, followed by flowing out from the second fluid outlet 37. In this flow, the engine cooling water exchanges heat with the refrigerant flowing in the return flow paths 26 of the first fluid path unit 10.

As described above, the heat exchanger according to this embodiment includes: a first fluid path unit 10 having a flow path extending in the direction (X direction) of the first fluid flowing toward the folded portions 27, 28 and at least two return flow paths 26 stacked continuously with the second fluid flowing in opposite directions by changing the direction at the folded portion 27, 28; a U-shaped flow path 34 arranged between the return flow portions 26, including a flow path in which the second fluid crossing the first fluid flows from the inlets 34 a, 34 c, 34 e, 34 g in the direction (counter Y direction) substantially perpendicular to X direction, the U-shaped flow path 34 being in opposed relation to the flow path in which the second fluid turns back and changing in the direction, reaches the outlets 34 b, 34 d, 34 f, 34 h; and a folded member 35 having the second fluid inlet 36 and the second fluid outlet 37 and connected to the inlets 34 a, 34 c, 34 e, 34 g and the outlets 34 b, 34 d, 34 f, 34 h; wherein the second fluid inlet 36 and the second fluid outlet 37 communicate with each other through all the U-shaped flow paths 34 connected to the folded member 35.

With this configuration, by carrying out the operation of moving the U-shaped flow paths 34 in one direction with respect to the first fluid path unit 10 and connecting the U-shaped flow paths 34 to the folded member 35, a heat exchanger high in productivity can be obtained in which the two fluid paths can be integrally assembled.

Also, in the case where the return flow paths 26 and the U-shaped flow paths 34 are coupled to each other by brazing, the heat resistance between the first and second fluids can be reduced for an improved heat exchange performance.

The U-shaped flow paths 34 are formed of U-shaped flat tubes communicating with each other in the stacking direction (Z direction) of the return flow paths 26, and the open inlets and outlets of a plurality of the U-shaped flat tubes arranged in Z direction are inserted between the return flow paths 26 and further connected to the connection ports of the fold member 35. In the case where this configuration is employed, the second fluid path unit is configured of component parts comparatively simple in shape, and therefore a heat exchanger high in machinability and easy to assemble is provided.

Other Embodiments

In the first, second and third embodiments described above, the gap between the return flow paths 26, i.e. the size h shown in FIG. 10 may be larger than the size of the return flow paths 26 in the stacking direction, i.e. the size t shown in FIG. 10. In the case where this configuration is employed, the folded portions 27, 28 of the flow paths of the first fluid path unit 10 are prevented from undergoing a sharp change in shape. Thus, the first fluid paths are not extremely curved, and therefore the machinability is improved for a higher productivity.

In the first, second and third embodiments described above, the second fluid paths 22, 23, 32 a to 32 g, 34 may be coupled by brazing with the first fluid path 26 by forming a partial joint on the outer surfaces of the respective flow paths as shown in FIG. 11. In a specific configuration for forming a partial joint on the outer surfaces of the respective flow paths, the outer profile of the second fluid path 26 may be roughened or corrugated and brought into point or line contact with the first flow path. On the contrary, the outer profile of the first fluid path may be corrugated or formed in rough surface and brought into contact at a plurality of points or in line contact with the second fluid path. In the case where this configuration is employed, the outer surfaces of the respective flow paths are coupled by brazing in such a manner as to form partial joints on the outer surfaces of the respective flow paths. In this way, the coupling by brazing is possible with a reduced variation such as a void of the brazed portions. Also, in the case where high-pressure fluid leaks, a leakage space can be formed to prevent the high-pressure fluid from mixing with the low-pressure fluid.

Further, a space B in contact with the atmosphere may be formed at each end of the partial joint shown in FIG. 11 along the direction of the main surface (the direction substantially perpendicular to the direction of flow of the first fluid) of the flat first fluid path 26, and a sacrifice corrosion layer 38 adapted to be corroded first may be formed in the partial joint. FIG. 12 is a sectional view taken in line A-A in FIG. 11, schematically indicating the cross section of the joint between the first fluid path 26 and the second fluid paths 22 f, 22 g in the direction of the main surface of the first fluid path 26. If this configuration is employed and a hole is formed by corrosion or the like in one of the fluid paths, the sacrifice corrosion layer 38 is corroded first so that the fluid leaking into the leakage space is released into the atmosphere, thereby preventing the corrosion of the other fluid path. This effectively prevents the high-pressure fluid from intruding into the flow path of the low-pressure fluid.

The heat exchanger according to the third embodiment described above may alternatively be configured as described below. Specifically, as shown in FIG. 13, the U-shaped flat tubes 42, 43, 44, 45, 46, 47 similar to the U-shaped flow paths 34 shown in FIG. 9 are arranged in two rows in the direction (X direction) of the flow of the first fluid. The U-shaped flat tubes 42, 43, 44 in the first row and the U-shaped flat tubes 45, 46, 47 in the second row are arranged with the connecting positions thereof staggered with respect to the fold members 48, 49, 50, 51, 52 along the stacking direction (Z direction), and one open end of each U-shaped flat tube is passed between the return flow paths 26 a to 26 f and connected to the corresponding connection port of the fold member 35.

Next, the configuration of the heat exchanger shown in FIG. 13 will be explained in detail. The fold members 48 to 52 each function as a tank and provide a cylindrical container having two connection ports arranged in X direction for connection with the corresponding U-shaped flat tube. The fold members 48 to 52 are formed of plate members of aluminum or aluminum alloy and are combined and coupled by brazing. The fold member 48 located uppermost in Z direction has a connection port 48 a adapted for connection with the outlet 42 b of the U-shaped flat tube 42 having the second fluid inlet 42 a after being inserted in Y direction between the return flow paths 26 a and passed between the flow paths (hereinafter expressed as “after being inserted”), and also has a connection port 48 b communicating with the connection port 48 a. The inlet 45 a of the second uppermost U-shaped flat tube 45, arranged in the second row and displaced downward of the U-shaped flat tube 42, is connected to the connection port 48 b after being inserted in the Y direction in the gap 26 a between the return flow paths. The fold member 49 arranged adjacently under the fold member 48 has, under the connection port 48 a, a connection port 49 a which is connected after the inlet 43 a of the U-shaped flat tube 43 located adjacently under the U-shaped flat tube 42 is inserted, in the Y direction, into the gap 26 b between the return flow paths, and also has a connection port 49 b communicating with the connection port 49 a on the side thereof. The connection port 49 b is located under the connection port 48 b and connected after the outlet 45 b of the U-shaped flat tube 45 is inserted in Y direction into the gap 26 b between the return flow paths. The fold member 50 arranged adjacently under the fold member 49 has, under the connection port 49 a, a connection port 50 a which is connected after the outlet (not shown) of the U-shaped flat tube 43 is inserted in Y direction into the gap 26 c between the return flow paths, and also has a connection port 50 b communicating with the connection port 50 a on the side thereof. The connection port 50 b is located under the connection port 50 b and connected after the inlet 46 a of the U-shaped flat tube 46 is inserted in Y direction into the gap 26 c between the return flow paths. The fold member 51 arranged adjacently under the fold member 50 has, under the connection port 50 a, a connection port 51 a which is connected after the inlet (not shown) of the U-shaped flat tube 44 located adjacently under the U-shaped flat tube 43 is inserted in Y direction into the gap 26 d between the return flow paths, and also has a connection port 51 b communicating with the connection port 51 a on the side thereof. The connection port 51 b is located under the connection port 50 b and is connected after the outlet 46 b of the U-shaped flat tube 46 is inserted, in the Y direction, into the gap 26 d between the return flow paths 26 d. The fold member 52 arranged adjacently under the fold member 51 has, under the connection port 51 a, a connection port 52 a which is connected after the outlet (not shown) of the U-shaped flat tube 44 is inserted in Y direction into the gap 26 e between the return flow paths, and also has a connection port 52 b communicating with the connection port 52 a on the side thereof. The connection port 52 b is located under the connection port 51 b and connected after the inlet 47 a of the U-shaped flat tube 47 is inserted in Y direction into the gap 26 e between the return flow paths. Further, the outlet 47 b of the U-shaped flat tube 47, after being inserted in Y direction into the gap 26 f between the return flow paths, is arranged under the fold member 52 and functions as an outlet of the second fluid path unit, so that the second fluid arriving through the U-shaped flow paths 42 to 47 and the fold members 48 to 52 is sent to other devices. The return flow path 26 and the U-shaped flow paths 42 to 47, after securing the joint between them by applying an external force from the vertical sides of the heat exchanger using a jig or the like, are fixedly coupled by brazing. In similar fashion, the outlets and the inlets of the U-shaped flow paths 42 to 47 and the connection ports of the fold members 48 to 52 are also coupled by brazing. Also, the sizes of the gaps 26 a to 26 f between the return flow paths are larger than the height of the flow path in Z direction of the U-shaped flow paths 42 to 47. This size difference makes it possible to easily carry out the job of inserting the U-shaped flow paths 42 to 47 into the corresponding gaps 26 e to 26 f between the return flow paths when assembling the first fluid path unit 10, the U-shaped flow paths 42 to 47 and the fold members 48 to 52.

The first fluid path unit 10 and the second fluid path unit configured of the U-shaped flow paths 42 to 47 and the fold members 48 to 52 having this configuration are integrally formed as one box-like object and make up a heat exchanger having considerable overall strength. In the case where the heat exchanger having this configuration is employed, the flow paths of the second fluid path unit can be lengthened and, therefore, the heat exchange performance is improved.

The flow paths of the second fluid path unit 53 of the heat exchanger according to the first embodiment, as shown in FIG. 14, may be configured of pipes having a circular cross section. The pipes having a circular cross section are formed of aluminum or aluminum alloy by extrusion molding or the like. The second fluid path unit 53 includes U-shaped flow paths stacked in seven stages having seven folded portions 53 c, 53 d, 53 e, 53 f, 53 g, 53 h, 53 i so that the second fluid inlet 52 a formed at an end of the flow path communicates with the second fluid outlet 53 b formed at the other end of the flow path. The first fluid inlet 53 a and the second fluid outlet 53 b are arranged on the side far from the position where the seven folded portions 53 c to 53 i are formed. The first fluid path unit 10 and the second fluid path unit 53 are assembled in such a manner that the second fluid paths are inserted, with the seven folded portions 53 c to 53 i first, deeply between the return flow paths 26 of the first fluid path unit 10 and the first and second fluid paths are opposed to each other, after which the joint between them is formed by applying an external force from the two vertical sides of the heat exchanger using a jig or the like, following by coupling by brazing. In assembled state, the direction (Y direction) of the second fluid crosses the direction (X direction) of the first fluid. The second fluid paths are inserted between the return flow paths 26 specifically through such steps that the folded portions 53 c, 53 d, 53 e, 53 f, 53 g, 53 h, 53 i are arranged at the side ends of the gaps 26 a, 26 b, 26 c, 26 d, 26 e, 26 f, 26 g, respectively, of the return flow paths 26, and then the second fluid path unit 53 is pushed in deeply in Y direction in FIG. 14. In the case where the heat exchanger having this configuration is employed, the number of parts making up the flow paths of the second fluid path unit 53 can be reduced and so can the cost of the heat exchanger.

In the heat exchanger according to the first embodiment, as shown in FIG. 15, the flow paths of the second fluid path unit 54 may be configured of flat tubes. The flat tubes are formed of aluminum or aluminum alloy by extrusion molding or the like. The flat tubes making up the second fluid path have a flat surface in opposed relation to the outer surface of the return flow paths 26 of the first fluid path unit 10. The second fluid path unit 54 has the U-shaped flow paths stacked in seven stages having seven folded portions 54 c, 54 d, 54 e, 54 f, 54 g, 54 h, 54 i in such a manner that the second fluid inlet 54 a formed at an end of the flow path and the second fluid outlet 54 b formed at the other end of the flow path communicate with each other. The first fluid inlet 54 a and the second fluid outlet 54 b are arranged on the side far from the seven folded portions 54 c to 54 i. The first fluid path unit 10 and the second fluid path unit 54 are assembled in such a manner that the second fluid path is inserted, with the seven folded portions 54 c to 54 i first, deep between the return flow paths 26 of the first fluid path unit 10 and then, after placing the first and second fluid paths in opposed relation to each other, the joint between them is formed by applying an external force from the vertical ends of the heat exchanger using a jig or the like, followed by coupling by brazing. In the assembled state, the direction (Y direction) in the second fluid flows crosses the direction (X direction) in which the first fluid flows. The second fluid path is inserted through specific steps in which the folded portions 54 c, 54 d, 54 e, 54 f, 54 g, 54 h, 54 i are applied against the side end portions of the gaps 26 a, 26 b, 26 c, 26 d, 26 e, 26 f, 26 g, respectively, between the return flow paths 26, and then the second fluid path unit 54 is pushed in deep along Y direction in FIG. 15. In the case where the heat exchanger having this configuration is employed, a compact heat exchanger can be obtained in which the required sectional area of the flow paths of the second fluid path unit 54 can be secured while at the same time reducing the length of the return flow paths 26 in stacking direction (Z direction).

While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art, without departing from the basic concept and scope of the invention. 

1. A heat exchanger comprising: a first fluid path unit including at least two return flow paths, in opposed relation to each other, having a flow path extending in the direction (X direction) in which the first fluid flows toward folded portions and a flow path in which the flow changes the direction at the folded portions, the return flow paths being stacked continuously; and a second fluid path unit having second fluid paths in which a second fluid flows across the first fluid are stacked through communication units in the same direction as the stacking direction (Z direction) of the return flow paths, and the second fluid paths thus stacked being each arranged between the return flow paths; wherein the second fluid paths each include a U-shaped flow path in which the second fluid flows in the direction (Y direction) substantially perpendicular to the flow (X direction) of the first fluid on the surface substantially perpendicular to the stacking direction (Z direction), and after turning back at one end of the second fluid path unit, flows in the opposite direction to the substantially perpendicular direction (Y direction), and wherein the communication units communicate with the U-shaped flow paths and are arranged at the other end of the second fluid path unit.
 2. A heat exchanger according to claim 1, wherein the flow paths making up the first fluid path unit are flat tubes having a longitudinal surface extending in the direction (Y direction) of flow of the second fluid between the return flow paths.
 3. A heat exchanger according to claim 2, wherein the flat tubes are flat tubes having many bores formed by extrusion molding.
 4. A heat exchanger according to claim 1, wherein the size of the gap between the return flow paths making up the first fluid path unit is larger than the size of the return paths in the stacking direction.
 5. A heat exchanger according to claim 1, wherein the return flow paths and the second fluid paths are coupled by being brazed to each other.
 6. A heat exchanger according to claim 5, wherein the second fluid paths and the first fluid paths are coupled by being brazed to each other by forming a partial joint on the outer surfaces of the flow paths.
 7. A heat exchanger according to claim 6, wherein a sacrifice corrosion layer corroded first is formed on the partially formed joint, and a space in contact with the atmosphere is formed at the end portion in the direction (Y direction) substantially perpendicular to the direction (X direction) of flow of the first fluid.
 8. A heat exchanger according to claim 1, wherein the second fluid path unit is formed by stacking plate members.
 9. A heat exchanger according to claim 8, wherein fins are arranged in the second fluid paths making up the second fluid path unit.
 10. A heat exchanger according to claim 1, wherein the second fluid paths are formed of a pipe having a circular section.
 11. A heat exchanger according to claim 1, wherein the second fluid paths are configured of flat tubes having a flat surface in opposed relation to the outer surface of the return flow paths.
 12. A heat exchanger comprising: a first fluid path unit including at least two return flow paths, in opposed relation to each other, having a flow path extending in the direction (X direction) in which the first fluid flows toward folded portions and a flow path in which the flow changes the direction at the folded portions, the return flow paths being stacked continuously; and a second fluid path unit having second fluid paths in which a second fluid flows across the first fluid are stacked through a communication unit in the stacking direction (Z direction) of the return flow paths, and each of the second fluid paths stacked being each arranged between the return flow paths; wherein the second fluid paths each include a U-shaped flow path in which the second fluid flows in the direction (Y direction) substantially perpendicular to the flow (X direction) of the first fluid, and after changing the direction, moving in the stacking direction (Z direction) and turning back at one end of the second fluid path unit, flows in the opposite direction to the substantially perpendicular direction (Y direction), and wherein the communication units communicate with the U-shaped flow paths and are arranged at the other end of the second fluid path unit.
 13. A heat exchanger according to claim 12, wherein the flow paths making up the first fluid path unit are flat tubes having a longitudinal surface extending in the direction (Y direction) of flow of the second fluid between the return flow paths.
 14. A heat exchanger according to claim 13, wherein the flat tubes are flat tubes having many bores formed by extrusion molding.
 15. A heat exchanger according to claim 12, wherein the size of the gap between the return flow paths making up the first fluid path unit is larger than the size of the return flow paths in the stacking direction.
 16. A heat exchanger according to claim 12, wherein the return flow paths and the second fluid paths are coupled by being brazed to each other.
 17. A heat exchanger according to claim 16, wherein the second fluid paths and the first fluid paths are coupled by being brazed to each other by forming a partial joint on the outer surfaces of the flow paths.
 18. A heat exchanger according to claim 17, wherein a sacrifice corrosion layer adapted to be corroded first is formed on the partially formed joint, and at least a space in contact with the atmosphere is formed at the end portion in the direction (Y direction) substantially perpendicular to the direction (X direction) of flow of the first fluid.
 19. A heat exchanger according to claim 12, wherein the second fluid path unit is formed by stacking plate members.
 20. A heat exchanger according to claim 19, wherein fins are arranged in the second fluid paths making up the second fluid path unit.
 21. A heat exchanger according to claim 12, wherein a partitioning member is arranged in the second fluid paths and a U-shaped flow path with the flow turned back before and after the partitioning member is formed.
 22. A heat exchanger comprising: a first fluid path unit including at least two return flow paths, in opposed relation to each other, having a flow path extending in the direction (X direction) in which the first fluid flows toward folded portions and a flow path in which the flow changes the direction at the folded portions, the return flow paths being stacked continuously; a second fluid path making up U-shaped second fluid paths arranged between the return paths and having a first flow path in which the second fluid crossing the first fluid flows in from inlets and flows in the direction (counter Y direction) substantially perpendicular to the flow (X direction) of the first fluid and a second flow path turned back to change the direction of flow and reaches outlets, the first and second flow paths being in opposed relation to each other; and a fold member having a second fluid inlet and a second fluid outlet and connected to the inlets and the outlets; wherein the second fluid inlet and the second fluid outlet communicate with each other through all the second fluid paths connected to the fold member.
 23. A heat exchanger according to claim 22, wherein the flow paths making up the first fluid path unit are flat tubes having a longitudinal surface extending in the direction (Y direction) in which the second fluid flows between the return flow paths.
 24. A heat exchanger according to claim 23, wherein the flat tubes are flat tubes having many bores formed by extrusion molding.
 25. A heat exchanger according to claim 22, wherein the size of the gap between the return flow paths making up the first fluid path unit is larger than the size of the return flow paths in the stacking direction.
 26. A heat exchanger according to claim 22, wherein the return flow paths and the second fluid paths are coupled by being brazed to each other.
 27. A heat exchanger according to claim 26, wherein the second fluid paths and the first fluid paths are coupled by being brazed to each other by forming a partial joint on the outer surface of the flow paths.
 28. A heat exchanger according to claim 27, wherein a sacrifice corrosion layer adapted to be corroded first is formed on the partially formed joint, and a space in contact with the atmosphere is formed at the end portion in the direction (Y direction) substantially perpendicular to the direction (X direction) in which the first fluid flows.
 29. A heat exchanger according to claim 22, wherein the second fluid paths are configured of flat tubes having a flat surface in opposed relation to the outer surface of the return flow paths.
 30. A heat exchanger according to claim 22, wherein the second fluid path is formed of U-shaped flat tubes communicating in stacking direction of the return flow path, and an open end of each of a plurality of the U-shaped flat tubes arranged in the same direction (Z direction) is inserted between the corresponding return flow paths and further connected to the fold member.
 31. A heat exchanger according to claim 30, wherein the U-shaped flat tubes are arranged in two rows in the direction (X direction) in which the first fluid flows and the two rows of the U-shaped flat tubes are connected to the fold member at positions staggered in stacking direction (Z direction). 